For supervised image segmentation, and also for image modeling, iterative image reconstruction is a method used to reconstruct two-dimensional and three-dimensional images in certain imaging techniques. For example, in computed tomography an image may be reconstructed from projections of an object. A common feature of dual energy X-ray computed tomography, spectral X-ray computed tomography, and phase-contrast computed tomography is that the medical imaging system generates two or even more images of an object with different contrasts with sufficient geometric alignment.